Robotic systems are often used in applications that require a high degree of accuracy and/or precision, such as surgical procedures or other complex tasks. A surgical robot typically includes one or more robotic arms coupled to a surgical cutting tool. The arm is linked to a controller and a navigation or tracking system. Surgical robotic systems may include various types of robots and various types of control schemes including “autonomous” surgical robotic systems with actively constrained autonomous control and “interactive” surgical robotic systems with passively constrained haptic control. Actively and passively controlled surgical robotic systems may be used in many surgical fields, including various orthopedic and non-orthopedic procedures.
Actively controlled surgical robots essentially take the cutting tools out of the hands of the surgeon's hand, and instead, execute a procedure according to a predetermined plan that has been programmed into the memory of the controller. On the other hand, a passively controlled robotic arm provides the surgeon with the ability to direct the robot arm as desired within certain limitations. One form of a passive system is a haptically controlled robotic arm that provides the surgeon with tactile feedback as the tool engages the patient's anatomy or if the tool engages or begins to cross a predetermined virtual boundary. One goal of a haptically controlled surgical robotic system is to augment a surgeon's sensory feedback during a procedure, while preventing the surgical tool from crossing the virtual boundary that may be in the form of a predefined haptic path or geometric haptic volume.
Both actively controlled and passively controlled surgical robots are used for procedures that require a high degree of accuracy. For example, referring to FIGS. 1-3, in hip replacement surgery, a surgeon can use an actively or passively guided robotic arm 20 equipped with a semi-spherical reamer 23 to sculpt a semi-spherical indentation in the acetabulum 21, which is a cup-shaped socket in the pelvis 22. The acetabulum 21 receives a cup commonly referred to as an acetabular cup (not shown) that, in turn receives a resurfaced femoral head in a partial hip arthroplasty or, in the case of a total hip arthroplasty (THA), a ball portion of a hip implant.
In an actively controlled system, after an initial incision is made, the surgeon manipulates the robotic arm 20 to move a cutting tool or reamer 23 that is coupled to the robotic arm 20 into position near the acetabulum 21. Then, the active controls of the system take over and the robotic arm 20 and reamer 23 follow a predetermined course until the desired indention in the acetabulum 21 is completed.
In contrast, a passively constrained haptic system provides the surgeon with some, but limited control over the cutting tool. Specifically, under haptic control, the surgeon guides the robotic arm 20 and reamer 23 during the formation of the indentation in the acetabulum. As long as the surgeon maintains the cutting tool within predefined virtual cutting boundary that is typically defined by a straight line haptic path or geometric haptic volume, the surgeon can move the robotic arm with low friction and low inertia. However, the robotic arm provides haptic (or force) feedback that prevents the surgeon from moving the cutting tool beyond the virtual cutting boundary. Further, to avoid inaccurate placement of the acetabular cup, unintended reaming of healthy bone and/or inaccurate bone preparation, if the center of the reamer 23 is not maintained along the haptic path or within the haptic volume of the virtual cutting boundary, some controllers may not allow the reamer 23 to operate.
The above-described actively and passively controlled robotic systems, though useful for THAs and many other procedures, may not be optimally suited for related procedures that do not require a high degree of accuracy. For example, surgeons frequently remove osteophytes and irregular bone, as well as labrum and other soft tissue around the rim of the acetabulum to provide the access required for reaming the acetabulum accurately. Further, additional manual resection may be necessary while fitting the acetabular cup in the reamed acetabulum and afterwards, especially if some bone or tissue irregularities are created during the reaming and fitting of the cup.
In contrast to the accuracy requirements for a proper acetabulum reaming, removal of osteophytes, labrum, irregular bone and/or other unneeded tissue prior to reaming the acetabulum and during or after cup installation does not require a high degree of accuracy and could be quickly and easily completed by providing the surgeon with unrestricted control of the cutting tool. However, both actively and passively controlled systems do not provide the surgeon with this freedom from the surgical plan, and as a result, THAs and other types of actively or passively controlled surgical procedures take more time than necessary, thereby increasing operating room time.
Specifically, if a surgeon desires to follow an actively or passively controlled bone resection with a secondary manual resection to remove osteophytes, bone spurs, sharp edges, other non-uniformities and unnecessary tissue, the surgeon may need to first execute one or more of the following steps: (1) remove the robotic arm from the surgical site; (2) detach the cutting tool from the robotic arm for manual use; and/or (3) use a secondary manual cutting device. Any of these steps require additional time, costs and resources, including the use of additional anesthesia to complete the procedure. Further, the additional time required to complete the surgery increases the risk of vascular complications due to the use of tourniquets, increased risk of infection and other technical complications due to the use of additional devices and procedural steps. These additional steps also increase costs, use of operating room time and limit or prevent the surgeon from using his/her talents to perform corrective manual cutting during the robotic cutting process.
Therefore, there is a need for actively and/or passively controlled surgical robotic systems that can be used to perform constrained procedures that require a high degree of accuracy and related unconstrained procedures that do not require a high degree of accuracy in a more time efficient manner. While an orthopedic surgery is used as an example, this need exists for many other procedures, including other orthopedic procedures and non-orthopedic procedures.